Which is a disorder is characterized by being at least 15 percent below normal body weight

The current DSM criteria for binge/purge anorexia 

I would assume its Anorexia but I'm not 100% sure the percentage.

Anxiety, stress, or something like that

People need to distract themselves with actitives. they can also find a natural high. an example would be eating alot of meat. that meat can release dopamine to the brain which gives one a natural high feeling.